When a supplier says twelve to eighteen days, they usually mean production. The number that matters is the time between raising a purchase order and the carton being available at your dock, and that number is longer.
For stock references, the gap is manageable. For sterile references, it can double. Planning on the production figure is how sites end up air-freighting consumables in the last week of a quarter.
Where the days go
A sterile wipe made to order passes through six stages, each with its own queue.
- Material release: raw fabric and packaging confirmed against the specification.
- Production: cutting, folding, bagging, labelling.
- Sterilisation: loading, the EO cycle itself, and aeration to reduce residuals.
- Release testing: sterility, bioburden, packaging integrity, and the paperwork.
- Freight: consolidation, port handling, sailing time.
- Customs and delivery: clearance, haulage, and the receiving inspection.
Production is often the shortest of the six. Aeration and release testing are the stages that surprise buyers, because they are invisible in a quotation.
| Stage | Typical range | Variance driver |
|---|---|---|
| Material release | 3–7 days | Fabric availability |
| Production | 10–18 days | Line capacity, pack complexity |
| Sterilisation + aeration | 7–14 days | EO cycle scheduling, residual limits |
| Release testing | 5–10 days | Laboratory queue |
| Sea freight | 18–35 days | Route, port congestion |
| Customs + delivery | 3–8 days | Documentation quality |
A quotation that says 15 days and a delivery that takes 45 is not a lie; it is two different measurements. Ask which one the supplier is quoting.
The buffer, calculated
Safety stock is usually set as a percentage of monthly consumption. A better approach is to set it from the variance of the longest stage.
If sea freight ranges from 18 to 35 days, the 17-day spread is the risk you are carrying. A buffer of three weeks of consumption covers the common case; a buffer of two weeks covers the average and fails in the tail.
For sterile items, add the release-testing spread as well, because a failed sterility test does not just delay one lot — it triggers an investigation.
The calendar effects
Two periods distort lead times every year. The first is the Lunar New Year shutdown, which removes one to three weeks of production capacity and creates a queue on either side. Orders placed in the four weeks before the holiday are the ones that arrive late.
The second is the pre-holiday freight peak in the fourth quarter, when container space tightens and rates rise. Consumables are low-value per cubic metre, so they are the first to be rolled.
Place orders for the first quarter before the shutdown, and for the fourth quarter before the peak. It is not sophisticated; it is just early.
Dual sourcing without doubling inventory
Two qualified references, one primary and one fallback, reduce risk without doubling stock. Hold the fallback at a lower level — enough to cover four to six weeks — and rotate it slowly so it does not expire on the shelf.
The fallback must be genuinely equivalent, not merely similar. That means a specification comparison and a bench test, not a catalogue review. We cover the qualification process separately.
A practical planning rhythm
Review consumption monthly, not quarterly. Compare actual usage against the forecast and adjust the next order rather than the annual plan. Keep a visible lead-time table by reference, updated when the supplier notifies a change.
Then set the reorder point from the longest realistic lead time, not the quoted one. The difference is the buffer you did not know you needed.
Working with a supplier on dates
Ask for dates by stage, not a single number. A supplier who can say "production completes on the 12th, sterilisation loads on the 15th, release on the 24th" is managing the chain. A supplier who says "about three weeks" is quoting a feeling.
Then agree what happens when a stage slips. The useful clause is not a penalty; it is a notification window. If sterilisation is delayed by three days, you want to know on day one, not on the day the container misses its sailing.
Finally, separate the date you need from the date you would like. Operators plan around a delivery date; procurement plans around a reorder point. If both use the same number, one of them is wrong.
A simple dashboard
Five columns on one page: reference, current stock in weeks, open order quantity, expected arrival, and the longest recent lead time. Review it weekly. It takes ten minutes and replaces most of the emergency emails that consume a purchasing team's month.
Why is sterile lead time so much longer?
Sterilisation, aeration and release testing sit between production and shipment. Each has a queue and a validation requirement that non-sterile products do not carry.
Is air freight ever justified for consumables?
For a line stop, yes. For routine supply, the freight premium usually exceeds the carrying cost of a modest buffer.
How often should lead times be reviewed?
Quarterly, and whenever a supplier changes a material, a site or a sterilisation contractor. A lead time is a property of the chain, not the product.
Lead time planning is mostly the discipline of measuring the whole chain and ordering earlier than feels necessary. The sites that avoid shortages are rarely the ones with the best forecast; they are the ones with the fewest surprises.
